Tooth implants are either known as one-part constructions or as two-part constructions. In the two-part embodiment, firstly an artificial tooth root is implanted into the jaw bone and it is subsequently connected to a second component, the abutment stud. The connection to the abutment stud is either performed intraoperatively or after a healing phase of several weeks. If the connection point between artificial tooth root and abutment stud lies below the gum level, after the surgical covering with the mucosa, the tooth root can heal without stress. Therefore, secure healing, which is not disturbed by load-related micromovements, can be achieved in the bones. In cases in which a primary anchoring stability of the tooth root in the jaw bone permits healing which is free of micromovements under moderate load, an intraoperative mounting of the abutment stud can be performed. More rapid osseointegration of the tooth root can thus be achieved with sufficient primary stability because of the stimulation of the bone growth due to the mechanical stimuli.
The artificial tooth root of the two-part embodiment has a connecting mechanism for this purpose, by means of which the abutment stud can be mechanically connected fixedly to the tooth root. Known embodiments are formfitting connections, for example, hexagonal or octagonal connections secured using screws, or, alternatively, cone connections. The abutment stud carries the later dental-prosthetic construction, which is mounted either fixedly or removably.
Screw-shaped geometries (WO 2008/128756 A2) or cylindrical geometries (EP 0 657 144 A1) are frequently used as implant forms for the artificial tooth root, wherein in most applications the screw-shaped anchor is preferred, because of the advantages in the primary stability and the simplicity of the handling.
Titanium alloys have become established as materials for the components of the two-part systems, which are provided in the region of the artificial tooth root with rough, porous surfaces, which promote the osseointegration, by means of various technologies. In addition to the macrostructure and microstructure, calcium phosphate coatings of greatly varying crystallography and morphology are known as layers which promote the bone apposition.
After completed implantation, an abutment stud which is sought out for size and orientation can be used in the two-part implants. The alignment of the artificial tooth root, which is oriented according to the conditions of the jaw bone, is therefore independent of the alignment of the prosthetic abutment, which is oriented according to the conditions of the artificial tooth. In addition, these abutment studs can be adapted to a small extent by means of grinding processing.
The constructions which are used for the connection between artificial tooth root and abutment stud have to transmit the substantial chewing forces which are introduced via the dental-prosthetic construction into the abutment stud. In this case, both axial forces and lateral forces and also tilting torques and rotation torques act on this connection. One embodiment is known, for example, from DE 196 33 570 C1. A plug connection is described here, which is secured against rotation using radially applied grooves. Such connections are often clamped using a central screw.
Further embodiments are non-self-inhibiting conical plug connections, which are secured by means of interlocking hexagonal or octagonal connections against rotation and which are also installed using a central screw. Such a connection is described, for example, in WO 2008/128756 A2. These formfitting connections, which are secured against twisting, do enable the simple transfer of the rotation position between a dental model and the situation in the mouth of the patient, but do not permit free selection of the rotation position of the abutment stud. Depending on the technical embodiment, six or eight possible positions are usually predefined. This is of particular significance in the case of the screw-shaped bony anchoring, since the rotation position of the implant results therein due to the implantation and is not freely selectable.
An embodiment which enables a free selection of the rotation position of the abutment stud in relation to the artificial tooth root is described in EP 0 707 835 A1. A self-inhibiting cone connection is shown, which is secured using a central screw.
All of these installation connections are particularly critical with regard to the compromise between the smallest possible structural size, i.e., the smallest possible implant diameter, and the operational reliability. In addition to the security against loosening or fatigue fracture of the connection due to the cyclic chewing stress, high demands are to be placed on the leak-tightness, i.e., freedom from gaps, of this connection.
For manufacturing reasons, with the exception of the cone connection, all formfitting connections are subject to at least extremely small gaps. This applies for the unloaded state, but is increased markedly in the event of chewing-functional load. Constructions which are subject to gaps are easily populated with bacteria and thus act as loci, from which inflammations originate. Gap formation thus promotes bacterial contamination and may be correlated with the resorption of the cervical bone bed (Zipprich, H. et al.: Erfassung, Ursachen and Folgen von Mikrobewegungen am Implantat-Abutment-Interface [Detection, causes, and consequences of micromovements at the implant-abutment interface]. In: Zeitschrift Implantologie [Implantology magazine] 2007; 15(1), pages 31-46, Quintessenz Verlag).
In comparison, one-part implant systems are substantially simpler in the geometric design thereof, since a technical connection, which has to transmit the chewing forces with a high level of reliability, can be omitted. One-phase systems are therefore substantially more cost-effective. The design freedom in the cervical region is also not restricted by the necessity of a connection which occupies structural volume. Smaller implant diameters can therefore also be implemented using one-phase implants, with equal endurance strength.
In the case of cylindrical artificial tooth root geometries or other artificial tooth root geometries which are not to be inserted by means of a screwing movement, one-part tooth implants can be preformed, in the case of suitable materials, by bending in the region of the abutment stud or abutment region before the implantation. An adaptation of the alignment of the part accommodating the artificial tooth to the requirements of the prosthetic abutment can thus be performed. In the case of the screw-shaped tooth roots, which are advantageous for the anchoring, this is not possible because of the rotation position, which is predefined by the implantation position and which results by way of the screwing in up to a solid seat. However, an adaptation of the orientation of the coronal part (abutment region) after implantation by bending, because of the high forces which act on the bone bed during the bending, is not possible or is only possible in cases having very good anchoring conditions, i.e., with long lengths of the artificial tooth root and with good bone conditions. Generally, the use of shorter implants is indicated because of the jaw atrophy (usually also with softer bone quality), wherein bending after implantation would damage the bony bed.
One example of one-part implants are the leaf-shaped implants according to Linkow, as are described, for example, in DE 25 22 941 A1 (see also Hartmann, H.-J.: Vom Extensionsimplantat zur Hightech-Schraube [From the extension implant to the high-tech screw]. In: zm 99, issue 22A, 16, Nov. 2009, Deutscher Ärzte-Verlag).
Further implants are disclosed in DE 39 18 309 A1 (so-called Bauer screw), DE 32 41 963 C1 (so-called Münch screw made of ceramic material), and DE 37 26 616 C1 (so-called Ledermann screw).
Known implants are often not adapted in the structure thereof to a bending process in the anchored state or are also not provided for this purpose.
In addition to the material titanium, the materials aluminum oxide ceramic and cobalt alloys have also been used for one-part tooth implants, wherein these materials from the group of ceramics and cobalt alloys have not proven themselves because of the lesser suitability for osseointegration. The prior art are presently surfaces based on titanium, which are microstructured by coatings or by targeted partially acting ablation. In particular blasting and etching methods are used as ablation methods, frequently in combination.
Only a few specific instruments are known for adapting dental constructions or dental components by targeted deformation in conjunction with dental implants. An instrument is known from DE 39 18 309 A1, which can engage on a coronal implant end. In this document (see also Bauer, E.: Die K. S. I. Bauerschraube [The KSI Bauer screw], 1987, KSI-Bauer-Schraube GmbH), a one-part implant having a bending zone between a coronal part and an anchoring part is described, wherein the adaptation of the implant is performed by bending after the implantation using the above-mentioned instrument. However, bending after implantation is only possible in the case of this arrangement with very long anchoring geometries and very good bone quality. The implementation of shorter anchoring geometries, as is necessary in the region of the mandible posterior teeth or in the case of low alveolar ridge height, is not possible, since a shorter implant causes excessively high reaction forces during the bending, which result in damage to the bony bed. Damage to the bony bed is also to be expected upon use in softer bones.
A bending instrument for a fixation pin is described in British patent application GB 2 450 617 A.
A further bending instrument is known from EP 2 438 885 A1.
Some instruments are very complex to produce and handle. If known arrangements are used, to carry out the intraoral adaptation by bending, extensive exposure of the alveolar ridge in the region of the implant is often necessary. Disadvantages for the patient can be linked thereto, for example, as a result of local bone loss due to the preceding surgical exposure. The soft tissue and bleeding of the operation wound make it more difficult to securely position the bending instrument at the point provided for it.